Limit at negative infinity is the value that is approaching when is decreasing without bound.

An upper bound of the function is given by for and note that the function is positive for all . Put these together we get
Now if , clearly . By the Squeeze Theorem, the limit at negative infinity of your function must be . The same inequality can be applied to the case.

Hello
In both cases (infinity or -infinity), you devide the denominator and the numerator by the highest power in the denominator
In your problem, the highest power in the denominator is
So by deviding top and bottom by we will get:

By remembering that where a & b are constants and b>0, you see that the final answer is 0/1 = 0.